Aluminum base bearing



p 16, 1958 A. w. SCHLUCHTER 2,852,365

ALUMINUM BASE BEARING Filed Deg. 19, 1955 575a ALUMl/VUM Auor L540 0/?L540 ALLOY mvmrdn mdd zwwih aq?w ATTORNEY Unite States Patent ALUMINUMBASE BEARING Alfred W. Schluchter, Hazel Park, Micln, assignor toGeneral Motors Corporation, Detroit, Micln, a corporation of DelawareApplication December 19, 1955, Serial No. 561,974

3 Claims. (Cl. 75-148) This invention relates to bearings andparticularly to an aluminum base bearing having good corrosionresistance and excellent anti-score properties.

Aluminum and most of its alloys are generally quite unsuitable for usein bearings for ferrous metal parts because the aluminum tends to adhereto, or combine with, the ferrous metal, thereby causing scoring orseizing. I have found, however, that by suitable combination of alloyingconstituents, this difiiculty can be overcome and a bearing alloyproduced having not only anti-friction properties but othercharacteristics especially suitable in a bearing material. Many aluminumbase alloys, such as the type disclosed in Pat-ent No. 2,338,399, whichissued April 15, 1941, in the name of Alfred W. Schluchter, aresatisfactory bearing materials in most respects. However, many of thesealloys do not possess sufiicient resistance to corrosion to enable themto be satisfactorily used under highly acidic conditions, such as aresometimes found in lubricating oils during use. The bearing material ofthe present invention, therefore, is an improvement in that respect onthe alloy disclosed in the aforementioned patent.

Accordingly, a principal object of this invention is to provideanaluminum base bearing alloy which has excellent corrosion resistance, aswell as satisfactory hardness and high score resistance. A furtherobject of this invention is to provide a corrosion-resistant aluminumbase alloy which possesses desirable frictional properties when used aseither a cast alloy or a wrought alloy.

In accordance with my invention, therefore, the foregoing objects andadvantages are attained with an aluminum base alloy containing minorproportions of indium, silicon and silver. Inasmuch as an alloy of thiscomposition is a stronger metal than many of the aluminum alloysgenerally heretofore used for beating purposes, solid bearings may beformed from it and no backing of steel or similar metals is necessaryfor many applications. If desired, a bearing formed from my alloy may beadvantageously provided with a thin overlay of lead or a lead basealloy. Examples of these overlays include the lead-tin and lead-indiumalloys which are used for this purpose and in which lead is the majorconstituent. It is therefore obvious that, as Well recognized by thetrade, the term bearing is used herein as meaning an element whichperforms a bearing function regardless of the presence or absence ofsuch an overlay.

Thus I have found that satisfactory bearing properties are obtained withan alloy comprising, by weight, approximately 0.05% to 5% indium, 0.5%to silicon, 0.05% to 5% silver, and the balance substantially allaluminum. Various incidental impurities may be included in this alloy inthe usual small amounts without any substantial detrimental effects.Hence the term aluminum, as used herein, embraces the usual impuritieswhich are found in aluminum ingots of commercial grade or which areintroduced during the handling operations incident to ordinary meltingpractice. For

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example, iron, which together with silicon is found in commercialaluminum, may be present in amounts not greater than approximately 0.5%without causing any harmful results. For optimum results I have foundthat an alloy should be'used which consists essentially of 0.08% to 0.5%indium, 2.5% to 5% silicon, 0.2% to 1% silver, and the balancesubstantially all aluminum.

Under severe test conditions, alloys having the above composition showexcellent anti-friction properties so that bearings formed of this alloynot only do not score or gall when in contact with a rotating steelshaft, but neither the shaftnor the bearings show an appreciable amountof wear after long and severe use. I have also found that the resistanceof this alloy to cracking or crumbling is extraordinarily high.

The addition of indium greatly improves the corrosion resistance andscore resistance of the aluminum base bearing. Despite the fact that ithas been generally recognized that the addition of indium to aluminumcauses slight loss of strength, I have found that indium, in thepresence of silicon, may be beneficially introduced in amounts as largeas 5% without causing a measurable loss of strength. In fact, theresultant alloy is remarkably resistant to disintegration under impactor pounding such as occurs in severe bearing service. Moreover, thepresence of indium does not affect the hardness if the alloy issubsequently heat treated. Although the effect of indium on bothstrength and hardness is negligible in any event if added in quantitiesno greater than 5%, indium is a relatively soft metal and hence theindium content'should not be higher than this amount.

I have also found that an indium content greater than 5% tends to causethis element to segregate out and settle to the bottom of the castingduring the solidification thereof in the form of the apparently nearlypure metal. Thus, too high an indium content raises the cost of thealloy by increasing personnel expenses because of increased handlingcosts and the necessity of more detailed and careful supervision.Moreover, if the final aluminum base alloy is to be used as a wroughtalloy to form a bearing, it is particularly important that the indiumcontent does not exceed approximately 0.5 inasmuch as greater amounts ofindium make the alloy too brittle. Therefore, in order that the materialmay be properly rolled, the indium content should not exceed the aforementioned maximum amount.

There is a marked improvement in score properties if indium is added inquantities up to 0.5 but increasing the indium content beyond thisamount does not proportionately increase the score resistance of thealloy. Hence, I prefer to use about 0.08% to 0.5% indium. An indiumcontent of at least 0.05% should be used in all instances to provideadequate score resistance.

The inclusion of silicon in my aluminum base bearing alloy also enhancesits score resistance. This property of silicon, plus the manner in whichit influences the effects of the indium present in the alloy and thefact that solidification shrinkage is lower as the silicon content israised, dictates that the alloy contain at least 0.5% silicon. Inasmuchas a high silicon content increases the brittleness of the final alloyand interferes with rolling processes, however, the maximum amount ofsilicon to be added necessarily is governed by the method in which thebearing is formed. Accordingly, silicon should not be present in amountsgreater than approximately 5% in the wrought alloy because such an alloyneeds to be rolled, while it may be added in amounts as high as about10% in the cast alloy. While an increased silicon content improves scoreresistance, the addition of silicon in amounts greater than 5% providesonly slight additional beneficial properties in this respect.Accordingly, best results are obtained for most purposes when thesilicon content is kept within a preferred range of 2.5% to 5%.

The score properties of the alloy are further improved by the presenceof silver. However, since silver is an expensive and relatively raremetal, it is desirable to add only as much of this metal as is necessaryto produce the desired results.

An example of the above alloy which possesses the aforementioneddesirable characteristics to an outstanding degree, therefore, is oneconsisting of 0.5% indium, 3% silicon, 0.5% silver, and the balancesubstantially all aluminum. As hereinbefore stated, various incidentalimpurities may be present in the above alloy, but for best results theamounts of these other elements should be confined to relatively lowproportions.

In order to obtain the high degree of resistance to pounding, such as isencountered in a bearing, it is preferable that the alloy have aphysical structure typified by the absence of continuous networks ofrelatively brittle eutectic mixtures. Conventional alloy procedures maybe employed with intermediate alloys, such as aluminumsilicon, beingused to introduce the silicon. For example, I have found that thealuminum and silicon may advantageously be fused at a temperature in theorder of approximately 1200 F., the melt then preferably being removedfrom the furnace. The silver and indium next may be successively orsimultaneously added to the melt, whichis subsequently stirred and cast,usually in metal or graphite molds. Casting temperatures below 1400 F.have proved to be satisfactory. The alloy may be either cast in thedesired form for use in bearings or it may be cast in ingots, rolleddown to strip material of the desired thickness, and bearing liners orother bearing elements formed from the rolled stock.

Cast articles having a metallographic structure showing a continuousnetwork of segrated metal compounds may be improved as to strength andfatigue resistance by suitable heat treatrnent. For example, I havefound that a solution treatment at a temperature between approximately800 F. and 1100" F. for a period of five to twenty hours is particularlyeffective to increase the amount of constituent elements in solidsolution. Upon removing the alloy from the furnace following thesolution treatment, it is preferable to cool it immediately by quenchingin water. This treatment provides the alloy with the high degree ofductility, such as is desirable for 4 rolling operations; and it maythen be easily rolled down to strip material of the desired thickness.

The above-described bearing has better resistance to fatigue and tocracking under pounding action than tinbronze bearings. Hence mybearings may be used as connecting rod bearings and main bearings for anautomobile engine. In addition, this hearing is highly resistant tocorrosion by acid constituents of lubricating oils which attack manyother bearing compositions.

A slipper or sleeve bearing embodying the invention described above isshown in the accompanying drawing. This bearing 10 comprises an aluminumbase alloy layer 12 of the composition hereinbefore set forth having asteel backing 14. The aluminum alloy in the bearing shown is providedwith a thin overlay 16 of lead or lead alloy as previously described.

It is to be understood that, while the invention has been described inconjunction with certain specific examples, the scope of the inventionis not to be limited thereby except as defined in the appended claims.

I claim:

1. A hearing formed of an alloy comprising approximately 0.05% to 5%indium, 0.5% to 10% silicon, 0.05 to 5% silver, and the balancesubstantially all aluminum.

2. A corrosion-resistant bearing formed of an alloy capable of beingrolled into sheet form from cast ingots and having high anti-frictionproperties and fatigue resistance, said alloy consisting essentially of0.08% to 0.5% indium, 2.5% to 5% silicon, 0.2% to 1% silver, and thebalance substantially all aluminum.

3. A bearing characterized by high anti-friction properties andresistance to disintegration under impact, said bearing being formed ofan alloy consisting of 0.05% to 5% indium, 2.5 to 5% silicon, 0.05% to5% silver, iron not in excess of 0.5%, and the balance substantially allaluminum, the physical structure of said alloy being substantially freeof continuous networks of segregated metallic constituents.

References Cited in the file of this patent UNITED STATES PATENTS1,079,035 Tebetts Nov. 18, 1913 1,908,023 Kempf May 9, 1933 2,746,136Rich May 22, 1956

1. A BEARING FORMED OF AN ALLOY COMPRISING APPROXIMATELY 0.05% TO 5%INDIUM, 0.5% TO 10% SILICON, 0.05% TO 5% SILVER, AND THE BALANCESUBSTANTIALLY ALL ALUMINUM.